The lab wants to try to manufacture longer ropes of the muscle, so it can weave a protective fabric for firefighters’ uniforms.

The fabric would automatically seal its pores when faced with a sudden flash, Baughman said.

Baughman’s new muscles are made of ropes of carbon nanotubes, a super-tiny, high-tech material that researchers are adding to everything from water filters to experimental airplane parts.

Baughman said he and his team twisted the nanotubes -- “quite similarly to the way people insert twists into common wool or cotton fibers” -- into thicker yarns. They then filled the hollow space in the nanotubes with different materials, including paraffin, the wax that goes in candles.

To get the muscles to contract, researchers heated them briefly. When heated, the paraffin wax expanded, pushing against the nanotube walls and making them fatter and shorter.

As the wax cooled again, it shrank, and the nanotubes became narrower and longer.

The muscles were able to shorten and then lengthen again every 25 milliseconds, or 25 thousandths of a second, Baughman said.

Such fast contractions mean the muscles are able to perform a lot of work, he said.